Hydraulic press

ABSTRACT

Hydraulic press including a frame with platens, at least one of which is carried or formed by a pressure plate structure adapted for transferring pressing force to an object between the platens, which press is adapted such that the pressure plate structure is substantially carried solely by horizontally adjustable supports mounted between the defining outer edges of such plate structure, such supports being positionally adjustable such that the surface of the corresponding platen assumes a predetermined shape during the pressing operation. The press suitably includes a mechanical mechanism for effecting the horizontal displacement in order to gain the desired positional adjustment of the supports.

This application is a continuation, of application Ser. No. 563,393,filed Nov. 9, 1983 now abandoned.

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to a hydraulic press, and moreparticularly to a hydraulic press having adjustable supports forproviding a platen surface thereof with a predetermined configurationduring the pressing operation.

Known hydraulic presses may often be referred to as either of two basictypes. In the one type they have a heavy frame, generally consisting ofparallel frames made from steelplate with a fixed platen or table, and amovable platen or table actuated by force generating means. The othertype includes two heavy plate or pressure beam structures, each of whichcan carry or form a platen or press table. The structures can be movedtowards, or away from each other with the aid of force-generating meansand yokes or C-shaped links. Although hereinafter briefly described,FIGS. 1a, 1b and FIG. 2 in the accompanying drawing are preliminarilyreferred to in this connection.

In FIG. 1 there are illustrated plate frames 1 with top portions 3 andbottom portions 5, while the numerals 7 and 9 respectively denote afixed and movable platen, the latter being actuated by hydrauliccylinders 11. In FIG. 2 the numerals 21 and 23 respectively denote topand bottom pressure plate structures with respective top and bottomplatens 25 and 27, while 29, 31 denote a yoke keeping the pressureplates 23 and 21 together. The plates 21 and 23 can be urged towardseach other with the aid of the yoke and hydraulic cylinders 33.

When forces are applied with the aid of the corresponding hydrauliccylinders the FIG. 1a frames 1 and the FIG. 2 members 21, 23 deflect ina manner exaggeratedly illustrated in FIGS. 3 and 4, respectively. Inmany cases this results in considerable drawbacks, e.g. in pressingrecords which must have a very uniform thickness, moulding goods inmoulds which must be kept parallel, deep-drawing sheet in presstools,shearing, edge folding of plates, tubes etc.

Different measures have been proposed for reducing the deflectionexemplified in FIGS. 3 and 4. The frames, pressure beam structures etc.can be made very stiff by increasing their material content, but this isan expensive solution that also increases the weight of the press. Thesurfaces can also be given an initial curvature by uneven heating of theframes, such as to keep deflection within acceptable limits when theforce is applied. This is however a solution that is relativelyexpensive, especially from an operational standpoint and is furthermoreonly usable in a restricted number of applications. It has also beensuggested to float the platen on a hydrostatic bed, which likewise is anexpensive solution in this case also requiring extra safety measures.

SUMMARY OF THE INVENTION

The present invention provides a generally utilizable principle forsatisfying prevailing desires regarding the shape of the platen pressingsurface during pressing in a high pressure press. A hydraulic press inaccordance with the invention includes a frame with platens, at leastone of the latter being carried or formed by a pressure plate structureadapted for enabling transmission of the pressing force to the object tobe pressed between the platens. The inventive press is distinguished inthat the pressure plate structure carrying or forming the platen isessentially carried solely by supports, positioned between the definingedges of the structure, these supports being positonally adjustable,such that the surface of the platen assumes a predetermined shape duringthe pressing operation.

In most cases, the desired pressing surface is as flat as possible, orfollows the shape of the other platen, which ensures uniform thicknessof the item produced as far as possible.

It should be emphasized that the pressure plate structure is to be freein respect of movements in the pressing direction in relation to thepress frame, i.e. not clamped or supported by it other than with theadjustable supports mentioned above. It is further emphasized thatcarrying the pressure plate structure on the press frame with the aid ofsaid supports should not have the character of a rigid attachment of thestructure relative to the frame, but instead should have the characterof free support relative to the frame.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in detail in the following, inconjunction with the accompanying drawings, wherein

FIGS. 1a and 1b illustrate the constructional principle of a press ofone type, and

FIG. 2 the constructional principle for another type,

FIGS. 3 and 4 illustrate the respective deflections during pressing forthe two types,

FIG. 5 is a schematic and partial illustration of a first embodiment ofa hydraulic press in accordance with the invention, illustrating theprinciple of movable supports for the pressure plate structure,

FIG. 6 shows an embodiment with a motor-driven apparatus for moving thesupports,

FIGS. 7a and 7b schematically illustrate the principle for a third andfourth embodiment, and

FIGS. 8 and 9 illustrate comparative values regarding calculations forthe deflection in a pressure beam structure for three loading cases.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The embodiment in accordance with the invention, illustratedschematically in FIG. 5 from one long side, of a high-pressure press,includes a frame 41 with vertical plates 43 on either side of a plane ofsymmetry 57 pertaining to the frame, bottom horizontal plates 45 unitingthe vertical plates on either side of the plane 57, and top(unillustrated) horizontal plates, similarly arranged. FIG. 5 only showsthe bottom portion of the press with the stationary platen. The top partwith the movable platen and hydraulic cylinders is not shown, but may beof the type illustrated in FIG. 1.

A plate structure is denoted by 47, e.g. mutually parallel plates in theplane of the paper in FIG. 5, with an upper, substantially flat surface49 forming or carrying the fixed platen of the press, and a lower,substantially flat surface 51, against which the support means orindividual supports 59, 61 engage, the latter being carried by a plate63 mounted on the lower horizontal plates 45 of the frame. The pressureplate structure 47 has vertical end surfaces or outwardly defining edges53 and 55, which are free in relation to the surrounding frame thesupports 59, 61 are mounted between such outwardly defining edges 53 and55. The supports 59, 61 are suitably made from bars with a suitablehomogenous cross section.

In accordance with the invention, the supports 59, 61 are movable to adesired distance from the central plane 57 of the press, i.e. within theperipheral confines of the outwardly defining edges of the structure 47.It will thus be possible to control deflection of the structure 47 whenit comes under load. For example, the deflection can be calculatedbeforehand with the aid of a computer, and thereby the appearance of theplaten upper surface 49, can be predetermined this being decisive forvariations in the thickness of the pressed item in the production oflamellar pressed goods, and the tolerances thereof in the stampingdirection during production of shaped goods. Ready computer programs forthis typical case are available. The folding angle for edge folding maybe calculated in a similar manner. The manual or other aids which may beutilized for moving the supports 59, 61 may be of different kinds knownin the art, and therefore only a version using the screw principle isillustrated in FIG. 6 by way of example.

The conditions for calculating the deflection of the pressure platestructure 47 for three loading cases, selected as examples, areillustrated in FIG. 8, the support 59 (as well as the support 61) havingthe configuration and placing or relative positioning depicted in theFigure, i.e. in FIG. 8. The height of the pressure plate structure is1000 mm. The total load is 18 MN in all three cases, although loaddistribution on the pressure platen 49 is different. The calculateddeflection of the pressure plate structure upper surface 49 in each ofthe three cases is seen on a larger scale in FIG. 9. Case II gives lessmaximum deviation X from the flat surface of the pressed item than CaseI, and in Case III the deviation is in the opposite direction inrelation to cases I and II.

The following data are applicable for the cases in FIGS. 8 and 9:

A=1000 mm

B=400 mm

C=980 mm

D=1930 mm

E=2490 mm

F=3050 mm

t=2×80 mm

Modulus of elasticity=210 00 N/mm²

v=0.3

The computer used was a LUCAS (R01041) 800425 (730 FL).

The calculations gave the following results:

Case I: X=0.3542 mm

Case II: X=0.0907 mm

Case III: X=0.4485 mm

Regarding the calculation of the deflection in accordance with theforegoing, it will be seen that in the three cases I, II and III thetotal load is the same and equal to 18 MN, but the load distribution onthe pressure platen 49 is different.

In case I the load is distributed over a length D=1930 mm, in case IIthe same load is distributed over a length E=2490 mm, and in case IIIthe same load is distributed over a length F=3050 mm, said loadingdistribution being symmetric vis-a-vis the plane of symmetry 57.

In FIG. 8 the support 59 is represented by an upward pressure,distributed over a length B=400 mm at a location on the lower side ofthe pressure plate structure as shown in FIG. 8. FIG. 8, of course, justshows the right half of the pressure plate structure; however, thesupport 61 is correspondingly placed under the left half of the pressureplate structure and the load distribution is the same in this latterhalf of the structure.

The positions of the support 59,61 represented by the upward pressureover the length B are of course the same in the three cases.

For the three cases described above, the deflection of the pressureplate structure upper surface 49 is calculated by the finite elementmethod, i.e. in the calculations the pressure plate structure is dividedinto a number of elements or zones. The results of these calculationsare shown in FIG. 9, which thus shows the calculated deflection of thepressure plate structure upper surface from a plane surface with thedeflections shown enlarged to make the Figure clearer.

In FIG. 9, of course, only the deflection in the right half of thepressure plate structure is shown, the deflection in the left halfthereof being equal thereto. The three described cases with threedifferent load distributions and fixed positions of the supports areequal with respect to the deflection of the pressure plate structureupper surface 49 to three different positions of the supports and aconstant load distribution, Thus, FIG. 9 illustrates the effect ofmoving the supports 59,61.

FIG. 6 illustrates how the supports 59, 61 in FIG. 5 may be displacedwith the aid of a motor 75 and an associated gear 77. The latter isconnected to a straight bar mounted in two bearings 71 and 73, andhaving two opposingly threaded sections 65 and 67, each positionallycontrolling a support 59, 61. It will be seen from the Figure that whenthe bar is rotated the supports will move just as much, but in oppositedirections relative to the plane of symmetry 57, accordingly assuringsymmetrical deflection of the structure 47. The motor 75 or gear 77 isprovided with control means for rotation reversal of the bar, andpossibly its rate of revolutions.

The bar may also be adapted for manual rotation, with or without areduction gear.

It is obvious that by applying the invention in each individual case, itis easy to determine beforehand the positions of the supports 59, 61giving the least possible deviation of the platen from the idealsurface. This surface may be completely flat, although such a conditionis not always necessary. FIGS. 7a and 7b schematically illustrate twoalternatives for supporting a pressure plate structure in accordancewith the invention. In FIG. 7a the structure 91 may be carried bysupports comprising two parts 93 and 95, mutually engaging at acylindrical or spherical interface 97, this arrangement providing forsmall angular variations between the structure 91 and the supportportion 99. Alternatively, as may be seen from FIG. 7b, the structure 91may be carried by through bolts 101.

The press types illustrated in FIGS. 1, 3, 5 and 7a, 7b are similar.However, the invention may also be applied to the type illustrated inFIGS. 2 and 4, by the introduction of a special pressure platestructure, forming or carrying the platen 27, and which is carried bythe bottom portion 23 of FIG. 2 with the aid of movable supports,according to the same principle depicted in FIGS. 5 and 6.

It should be noted that the number of movable supports for the pressureplate structure may be more than two, for further reducing the maximumdeflection of the structure during pressing operations.

It is also emphasized that the term "pressure plate structure" in itspresent context is not limited to relate to any special geometricalshape, since the dimensions of the structure and its interrelating sizesmay be varied greatly from case to case. The term thus includes suchstructures used in edge folding and the like.

The invention is this not restricted to the illustrated and describedembodiments, since thses may be varied and modified in many ways withinthe scope of the invention.

I claim:
 1. Hydraulic press comprising a frame having opposed platensprovided with platen surfaces positioned for relative movement towardand away from each other, in which at least one of the platens islocated on a pressure plate structure comprising mutually parallelplates having outwardly defining edges, said pressure plate structureconstituting means for transferring the pressing force of the press tothe article being pressed between the platens, and in which saidpressure plate structure is carried solely by a plurality ofhorizontally adjustable individual support means mounted between theoutwardly defining edges of said pressure plate structure and in whichsaid support means are horizontally displaceable to a predeterminedposition such that the corresponding platen surface assumes apredetermined configuration during the pressing operation.
 2. Hydraulicpress of claim 1, wherein two individual said support means are providedfor the corresponding said pressure plate structure.
 3. Hydraulic pressof claim 1, wherein the support means comprise bars.
 4. Hydraulic pressof claim 1, wherein the support means comprise beams.
 5. Hydraulic pressof claim 1, wherein said pressure plate structure comprises a pluralityof special steel plates.
 6. Hydraulic press of claim 1, wherein twoindividual said support means are provided for the corresponding saidpressure plate structure, and the mechanical means include a straightrotatable bar, having two opposingly threaded protions adapted forco-action with, and displacement of, an associated one of said supportmeans for effecting symmetrical movement of the support means toward andaway from each other along the rotatable bar.
 7. Hydraulic press ofclaim 1, wherein said at least one of the platens is carried by thecorresponding said pressure plate structure.
 8. Hydraulic press of claim1, wherein said at least one of the platens is formed by thecorresponding said pressure plate structure.
 9. Hydraulic press of claim1, wherein the support means are carried on an outer support portion ofthe frame remote from the corresponding said pressure plate structure,and each support means comprises a pair of co-acting parts mutuallyengaging at an interface therebetween and arranged for providing smallangular variations between the outer support portion of the frame andsaid pressure plate structure.
 10. Hydraulic press comprising a framehaving opposed platens provided with platen surfaces positioned forrelative movement toward and away from each other, in which at least oneof the platens is located on a pressure plate structure comprisingmutually parallel plates having outwardly defining edges, said pressureplate structure constituting means for transferring the pressing forceof the press to the article being pressed between the platens, and inwhich said pressure plate structure is carried solely by a plurality ofhorizontally adjustable individual support means mounted between theoutwardly defining edges of said pressure plate structure and which saidsupport means are provided with mechanical means for effecting thehorizontal displacement of the support means to a predetermined positionsuch that the corresponding platen surface assumes a predeterminedconfiguration during the pressing operation.
 11. Hydraulic pressaccording to claim 10, wherein two individual support means are providedfor the corresponding pressure plate structure.
 12. Hydraulic pressaccording to claim 10, wherein said support means comprise bars. 13.Hydraulic press according to claim 10, wherein said support meanscomprise beams.
 14. Hydraulic press according to claim 10, wherein saidpressure plate structure comprises a plurality of spaced steel plates.15. Hydraulic press according to claim 10, wherein two individual saidsupport means are provided for the corresponding said pressure platestructure, and the mechanical means include a straight rotatable bar,having two opposingly threaded portions adapted for co-action with, anddisplacement of, an associated one of said support means for effectingsymmetrical movement of the support means toward and away from eachother along the rotatable bar.
 16. Hydraulic press according to claim10, wherein said at least one of the platens is carried by thecorresponding said pressure plate structure.
 17. Hydraulic pressaccording to claim 10, wherein said at least one of the platens isformed by the corresponding said pressure plate structure.
 18. Hydraulicpress according to claim 10, wherein the support means are carried on anouter support portion of the frame remote from the corresponding saidpressure plate structure, and each support means comprises a pair ofcoating parts mutually engaging at an interface therebetween andarranged for providing small angular variations between the outersupport portion of the frame and said pressure plate structure.